Answer
The unknown length is $25$ feet.
Work Step by Step
Let $c$ = length of the hypotenuse
Use the Pythagorean theorem's formula $c^2=a^2+b^2$ where c= length of the hypotenuse, and a and b are the lengths of the legs of the right triangle to have:
$\\c^2=24^2+7^2
\\c^2=576+49
\\c^2=625
\\c = \sqrt{625}
\\c=25$
